AltaRock Energy taps the Earth's core for energy. Here are all the parts of the process. Roll over the numbers below to take a closer look.

HOT STUFF

Tapping the earth’s core for energy

Geothermal energy holds great promise as a renewable source of round-the-clock electricity. But large-scale geothermal power pro- duction, which involves harnessing energy generated by the heat of the earth’s interior, has proved difficult and expensive. AltaRock Energy of Seattle has developed a process that could be a breakthrough. The company’s enhanced geothermal system, or EGS, involves pumping clean water into naturally occurring fractures two to three miles below the earth’s surface, creating three reservoirs. There the water is heated to temperatures as high as 600 degrees Fahrenheit and pumped back up to a power plant to produce electricity. (Conventional systems are confined to locations with naturally occurring geothermal reservoirs.) Last June, AltaRock began work on an EGS project near the Newberry volcano in Deschutes National Forest in Oregon, installing equip- ment to monitor groundwater and seismic activity. The company, founded in 2007 by geothermal engineer Susan Petty, has raised more than $50 million in funding from venture capital firms, Google, and the U.S. Department of Energy. Petty expects the Oregon plant to begin producing 15 megawatts of electricity, enough to power 15,000 homes, by 2017.

WATER IS PUMPED BELOW THE EARTH'S SURFACE

Cold groundwater initially sourced from local wells is pumped 10,000 feet to 15,000 feet down an injection well into a system of fractures in the earth’s crust.

HOT ROCK HEATS THE WATER

The water flows into the fissures, opening them slightly and creating reservoirs of water heated to temperatures of 600 degrees Fahrenheit.

WELLS PUMP HOT WATER

Production wells pump the hot water and steam back up to a power plant aboveground.

POWER IS GENERATED

The steam and boiling water are separated after they reach the power plant. The steam turns turbines that power generators.

COOLED WATER IS PUMPED BACK DOWN

Hot water flows through an air- cooling tower that lowers its temperature. Then the water is pumped back into the injection well to restart the process.